THZ1 is primarily used in biomedical research as a potent and selective inhibitor of cyclin-dependent kinases (CDKs), especially CDK7. It is widely applied in studies related to transcription regulation and cancer biology. By targeting CDK7, THZ1 disrupts the phosphorylation of the RNA polymerase II carboxy-terminal domain, effectively suppressing global transcription. This property makes it a valuable tool for investigating the role of transcriptional addiction in various cancer cells, particularly in aggressive types such as triple-negative breast cancer, small cell lung cancer, and neuroblastoma. Researchers use THZ1 to probe the vulnerabilities of cancer cells that rely heavily on rapid gene expression. It has shown promising results in preclinical models by inducing apoptosis and reducing tumor growth. Additionally, THZ1 helps in understanding the broader implications of CDK inhibition on cell cycle progression and DNA damage response. Its application extends to combination therapy studies, where it is tested alongside other anticancer agents to enhance therapeutic efficacy and overcome drug resistance.